The Role of Microbiota and Immunobiotics in Granulopoiesis of Immunocompromised Hosts

Beyond probiotics, uses of their next-generation for poultry and humans: A review

The production of healthy food is one of the basic requirements and challenges. Research efforts have been introduced in the human's food industry to reduce the microbial resistance and use safe and healthy alternatives with a high durability. However, the conducted work about these issues in the field of livestock animal production have been started since 2015. Inappropriate and extensive use of antibiotics has resulted in the increase of antimicrobial resistance, presence of drug residues in tissues, and destruction of the gut microbiome. Therefore, discovering and developing antibiotic substitutes were urgent demands. Probiotic compounds containing living micro-organisms are important antibiotic alternative that have been beneficially and extensively used in humans, animals, and poultry. However, some probiotics show some obstacles during production and applications. Accordingly, this review article proposes a comprehensive description of the next-generation of probiotics including postbiotics, proteobiotics, psychobiotics, immunobiotics and paraprobiotics and their effects on poultry production and human's therapy. These compounds proved great efficiency in terms of restoring gut health, improving performance and general health conditions, modulating the immune response and reducing the pathogenic micro-organisms. However, more future research work should be carried out regarding this issue.

A metabolic perspective of the neutrophil life cycle: new avenues in immunometabolism

Neutrophils are the most abundant innate immune cells. Multiple mechanisms allow them to engage a wide range of metabolic pathways for biosynthesis and bioenergetics for mediating biological processes such as development in the bone marrow and antimicrobial activity such as ROS production and NET formation, inflammation and tissue repair. We first discuss recent work on neutrophil development and functions and the metabolic processes to regulate granulopoiesis, neutrophil migration and trafficking as well as effector functions. We then discuss metabolic syndromes with impaired neutrophil functions that are influenced by genetic and environmental factors of nutrient availability and usage. Here, we particularly focus on the role of specific macronutrients, such as glucose, fatty acids, and protein, as well as micronutrients such as vitamin B3, in regulating neutrophil biology and how this regulation impacts host health. A special section of this review primarily discusses that the ways nutrient deficiencies could impact neutrophil biology and increase infection susceptibility. We emphasize biochemical approaches to explore neutrophil metabolism in relation to development and functions. Lastly, we discuss opportunities and challenges to neutrophil-centered therapeutic approaches in immune-driven diseases and highlight unanswered questions to guide future discoveries.

Regulation of emergency granulopoiesis during infection

During acute infectious and inflammatory conditions, a large number of neutrophils are in high demand as they are consumed in peripheral organs. The hematopoietic system rapidly responds to the demand by turning from steady state to emergency granulopoiesis to expedite neutrophil generation in the bone marrow (BM). How the hematopoietic system integrates pathogenic and inflammatory stress signals into the molecular cues of emergency granulopoiesis has been the subject of investigations. Recent studies in the field have highlighted emerging concepts, including the direct sensing of pathogens by BM resident or sentinel hematopoietic stem and progenitor cells (HSPCs), the crosstalk of HSPCs, endothelial cells, and stromal cells to convert signals to granulopoiesis, and the identification of novel inflammatory molecules, such as C/EBP-β, ROS, IL-27, IFN-γ, CXCL1 with direct effects on HSPCs. In this review, we will provide a detailed account of emerging concepts while reassessing well-established cellular and molecular players of emergency granulopoiesis. While providing our views on the discrepant results and theories, we will postulate an updated model of granulopoiesis in the context of health and disease.

Vitamin D Enhances Neutrophil Generation and Function in Zebrafish (Danio rerio)

Vitamin D (VD) is a major regulator of calcium metabolism in many living organisms. In addition, VD plays a key role in regulating innate and adaptive immunity in vertebrates. Neutrophils constitute an important part of the first line of defense against invading microbes; however, the potential effect of VD on neutrophils remains elusive. Thus, in this study zebrafish in different developmental stages were utilized to identify the potential role of VD in the basal homeostasis and functions of neutrophils. Our results showed that addition of exogenous VD3 promoted granulopoiesis in zebrafish larvae. Reciprocally, neutrophil abundance in the intestine of adult zebrafish with a cyp2r1 mutant, lacking the capacity to 25-hydroxylate VD, was reduced. Moreover, VD-mediated granulopoiesis was still observed in gnotobiotic zebrafish larvae, indicating that VD regulates neutrophil generation independent of the microbiota during early development. In contrast, VD was incapable to influence granulopoiesis in adult zebrafish when the commensal bacteria were depleted by antibiotic treatment, suggesting that VD might modulate neutrophil activity via different mechanisms depending on the developmental stage. In addition, we found that VD3 augmented the expression of il-8 and neutrophil recruitment to the site of caudal fin amputation. Finally, VD3 treatment significantly decreased bacterial counts and mortality in zebrafish infected with Edwardsiella tarda (E. tarda) in a neutrophil-dependent manner. Combined, these findings demonstrate that VD regulates granulopoiesis and neutrophil function in zebrafish immunity.

Probiotics and Trained Immunity

The characteristics of innate immunity have recently been investigated in depth in several research articles, and original findings suggest that innate immunity also has a memory capacity, which has been named “trained immunity”. This notion has revolutionized our knowledge of the innate immune response. Thus, stimulation of trained immunity represents a therapeutic alternative that is worth exploring. In this context, probiotics, live microorganisms which when administered in adequate amounts confer a health benefit on the host, represent attractive candidates for the stimulation of trained immunity; however, although numerous studies have documented the beneficial proprieties of these microorganisms, their mechanisms of action are not yet fully understood. In this review, we propose to explore the putative connection between probiotics and stimulation of trained immunity.

The Role of Immunobiotics and Postbiotics in the Recovery of Immune Cell Populations From Respiratory Mucosa of Malnourished Hosts: Effect on the Resistance Against Respiratory Infections

Malnutrition is associated with a state of secondary immunodeficiency, which is characterized by a worsening of the immune response against infectious agents. Despite important advances in vaccines and antibiotic therapies, the respiratory infections are among the leading causes of increased morbidity and mortality, especially in immunosuppressed hosts. In this review, we examine the interactions between immunobiotics-postbiotics and the immune cell populations of the respiratory mucosa. In addition, we discuss how this cross talk affects the maintenance of a normal generation of immune cells, that is crucial for the establishment of protective innate and adaptive immune responses. Particular attention will be given to the alterations in the development of phagocytic cells, T and B lymphocytes in bone marrow, spleen and thymus in immunosuppression state by protein deprivation. Furthermore, we describe our research that demonstrated that the effectiveness of immunobiotics nasal administration in accelerating the recovery of the respiratory immune response in malnourished hosts. Finally, we propose the peptidoglycan from the immunobiotic Lactobacillus rhamnosus CRL1505 as the key cellular component for the effects on mucosal immunity, which are unique and cannot be extrapolated to other L. rhamnosus or probiotic strains. In this way, we provide the scientific bases for its application as a mucosal adjuvant in health plans, mainly aimed to improve the immune response of immunocompromised hosts. The search for safe vaccine adjuvants that increase their effectiveness at the mucosal level is a problem of great scientific relevance today.

Lactobacillus rhamnosus postbiotic-induced immunomodulation as safer alternative to the use of live bacteria

Many attempts have been made to search for safer immunomodulatory agents that enhance the immune response and reduce the number and severity of infections in at-risk populations. The use of postbiotics, non-viable microbial cells or cell fractions that confer a health benefit to the consumer, represents a safe and attractive way to modulate and enhance the immune function in order to improve human health. Therefore, the aim of this work is to evaluate the immunoregulatory effect of Lactobacillus rhamnosus CRL1505 postbiotics in a complex culture system using human intestinal epithelial cells (IECs) and dendritic cells (DCs) differentiated from peripheral blood mononuclear cells. First, we demonstrated that L. rhamnosus CRL1505 differentially modulate human IECs and DCs after the challenge with the TLR4 agonist LPS. The CRL1505 strain down-regulated CD40, CD80 and CD86 expression in DCs, and increased their production of TNF-α, IL-1β, IL-6 and IL-10. Interestingly, the non-viable strain was able to modulate the immune response of both types of human cells. Then, we showed that cell wall (CW1505) and peptidoglycan (PG1505) from L. rhamnosus CRL1505 modulated TLR4-triggered immune response in IECs and DCs. Of interest, CW1505 showed a strong stimulatory effect while the PG1505 presented immune characteristics that were more similar to viable and non-viable CRL1505. To date, several molecules of immunobiotics were identified, that can be connected to specific host-responses. We hereby demonstrated that peptidoglycan of L. rhamnosus CRL1505 is a key molecule for the immunobiotic properties of this strain in human IECs and DCs. Likewise, the result of these studies could provide predictive tools for the in vivo efficacy of postbiotics and the scientific basis for their future applications in immunocompromised patients.

Dexmedetomidine alleviates sleep-restriction-mediated exaggeration of postoperative immunosuppression via splenic TFF2 in aged mice

Major abdominal procedures could induce dysfunction in the immune system and lead to postoperative immunosuppression. Sleep dysfunction is associated with impaired immune activity. However, the effects of postoperative sleep dysfunction on postoperative immune function remain unclear. In this study, we found that sleep-restriction (SR) after surgery increased the spleen weight and the percentage of myeloid-derived suppressor cells (MDSCs) in the spleen, and inhibited splenic CD8⁺ T cells activity, which was via inhibiting subdiaphragmatic vagus nerve (SVN)-mediated trefoil factor 2 (TFF2) expression in the spleen of aged mice. Dexmedetomidine could alleviate SR-induced these changes via modulating gut microbiota, which acted through SVN. Moreover, we showed essential roles of splenic TFF2 in attenuating SR-induced reduced protective ability against Escherichia coli (E. coli) pneumonia, increased expression of IL-4 and IL-13 in the lung and M2 polarization of alveolar macrophages (AMs), and decreased phagocytic activity of AMs. Dexmedetomidine improved SR-induced reduced protective ability against E. coli pneumonia via splenic TFF2, and subsequently decreasing IL-4 and IL-13 expression in the lung via modulating gut microbiota/SVN, increasing the compromised phagocytic activity of AMs, and ultimately decreasing M2 polarization of AMs. Taken together, dexmedetomidine-induced increase in splenic TFF2 expresssion could alleviate SR-induced exaggeration of postoperative immunosuppression.

Antimicrobial-Induced Cytopenia and Bone Marrow Hypocellularity in Patients with Cirrhosis

There is great variation in cytopenias in cirrhotic patients with same severity and hypersplenism and their causative factors are not clear. Recent studies have highlighted the role of gut microbiome in regulation of constant and emergency hematopoiesis. Broad-spectrum antibiotics can disrupt the homeostatic or adaptive microbiota in cirrhosis, leading to impaired hematopoiesis and a higher susceptibility to infections. We studied all patients with cirrhosis with cytopenia (anemia, leucopenia, and/or thrombocytopenia), admitted in the Institute of Liver & Biliary Sciences, between January 2016 and July 2017, who underwent a bone marrow examination. The effect of the different antimicrobial agents on peripheral blood counts and bone marrow cellularity was assessed. A total of 196 patients' data was analyzed for this study. Patients on antimicrobials (n = 115) had significantly lower hemoglobin (p < 0.001), total leucocyte count (p = 0.048), and platelet count (p = 0.043) compared to patients not on antimicrobials. On unadjusted analysis, significant association with thrombocytopenia existed in beta-lactams (OR = 1.56, 95% CI = 1.06–2.40), quinolones (OR = 1.66, 95% CI = 1.11–2.61), and antifungals (OR = 2.24, 95% CI = 1.96–4.34). Cephalosporins were found to be significantly associated with anemia (OR = 1.91, 95% CI = 1.07–3.41). Patients who received antimicrobials had hypocellular marrow (p < 0.001) as compared to nonrecipients of antibiotics. The adjusted analysis showed that quinolones and beta-lactam antibiotics are the drug classes having significant association with thrombocytopenia and alternative class of drug should be explored in these patients to avoid severe thrombocytopenia.